1. Technical Field
The present invention relates to a prism structure and a projector.
2. Related Art
FIG. 8 is a diagram showing a system of a general type provided to a projector. In the accompanying drawings and descriptions below, a z axis is along the traveling direction of lights, an x axis is vertical to the z axis and parallel to the paper surface of FIG. 8, and a y axis is vertical to both the z axis the paper surface of FIG. 8.
As shown in FIG. 8, a projector 1000a is configured to include an illumination device 100, a color separation light guiding system 200, three liquid crystal devices 400aR, 400aG, and 400aB, a cross dichroic prism 500a, and a projection system 600. Specifically, the color separation light guiding system 200 separates a light coming from the illumination device 100 into three color lights of red, green, and blue. The liquid crystal devices 400aR, 400aG, and 400aB each generate an image light through modulation of, in accordance with image information, the three color lights as results of separation by the color separation light guiding system 200. The cross dichroic prism 500a combines the image lights generated by those three liquid crystal devices 400aR, 400aG, and 400aB. The projection system 600 projects the image light as a result of combination in the cross dichroic prism 500a onto a projection surface such as screen SCR.
In recent years, such a projector is often provided with a prism structure, which is a combination unit that includes the entire or part of components of liquid crystal devices, and a cross dichroic prism. The components of liquid crystal devices are exemplified by a liquid crystal panel, a light emitting-side polarizer, and others. For an exemplary projector of such a type, refer to Patent Document 1 (JP-A-10-10994 (FIG. 7)).
FIG. 9 is a diagram for illustrating such a prism structure 550b. 
As shown in FIG. 9, in the prism structure 550b, a liquid crystal panel 410bR specifically for red lights is retained by a liquid crystal panel retention frame 412bR in its concave portion. A cross dichroic prism 500b is affixed with a fixture frame 440bR on its light incident-side surface. The fixture frame 440bR is screwed with an intermediate frame 450bR.
The liquid crystal panel 410bR is put into the temporarily-screwed state through insertion and engagement of pins into each corresponding hole of the liquid crystal panel retention frame 412bR. The pins are each protruding from the corner of the intermediate frame 450bR. While being in the temporarily-screwed state, the liquid crystal panel 410bR is positioned by a pair of wedges 418bR and 418bR being pushed between the liquid crystal panel 410bR and the liquid crystal panel retention frame 412bR. These wedges 418bR and 418bR are eventually adhered for fixation to the fixture frame 440bR. Although not shown, other liquid crystal panels 410bG and 410bB are similarly subjected to such positioning and fixation so that the liquid crystal panels 410bR, 410bG, and 410bB are all positioned with precision.
The problem here is that, however, such a prism structure 550b requires a number of components including the fixture frame 440bR, the intermediate frame 450bR, the liquid crystal panel retention frame 412bR, the wedges 418bR and 418bR, and others. Assembling such many components also requires a lot of work and makes the processes complicated, and thus reducing the manufacturing cost is not that easy.
In consideration of the above, the inventor of the present invention has filed an application for the prism structure that can solve the above problems (JP-A-2005-234124).
FIG. 10 is a diagram for illustrating a prism structure 550c in the above related art. The prism structure 550c (partially not shown) is a combination unit with a part of components of liquid crystal devices 400cR, 400cG, and 400cB (partially not shown), and a cross dichroic prism 500c (not shown). The components here include a liquid crystal panel 410cR, and a light emitting-side polarizer 430cR. This prism structure 550c is configured to include a fixture member 440cR and a retention member 450cR. The fixture member 440cR is provided with a stand-up piece d1 each at both ends, and has the C-shaped cross section. The retention member 450cR is provided with a stand-up piece each at both ends, and also has the C-shaped cross section. The stand-up pieces d1 and d1 of the fixture member 440cR are so assembled as to slide in contact with the stand-up pieces d2 and d2 of the retention member 450cR.
In the prism structure 550c of such a configuration, after the fixture member 440cR is combined together with the retention member 450cR for fixation, the liquid crystal panel 410cR is attached and fixed to the cross dichroic prism 500c. This accordingly reduces the number of components required to attach the liquid crystal panel 410cR to the cross dichroic prism 500c, i.e., only the fixture member 440cR, and the retention member 450cR. As a result, the assembly procedure is simplified so that the manufacturing cost can be reduced.
The issue is that, with the prism structure 550c, the process remains complicated to dispose the light emitting-side polarizer 430cR with a right angle with respect to the liquid crystal panel 410cR and the cross dichroic prism 500c. This is due to the configuration that the light emitting-side polarizer 430cR is glued with adhesive to a light emitting-side surface d3 of the retention section 450cR.
The recently-popular liquid crystal device in a projector includes a viewing angle compensation plate or a second light emitting-side polarizer between a liquid crystal panel and a light emitting-side polarizer. This is aimed to increase the viewing angle characteristics, the contrast characteristics, and others. Similarly to the above-described case with the light emitting-side polarizer, such viewing angle compensation plate and second light emitting-side polarizer both fail in implementing a predetermined viewing angle or contrast if they are not correctly angled with respect to the liquid crystal panel and the cross dichroic prism.
The related art of JP-A-2005-234124 presents no description, not in the specification or in the accompanying drawings, about how to correctly angle the viewing angle compensation plate or the second light emitting-side polarizer with respect to the liquid crystal panel 410cR, the cross dichroic prism 500c, and others.